A patient's target intensity is moderate. Which HRR range should the PT prescribe?

• A. 40-59%
• B. 20-39%
• C. 60-89%
• D. ≥90%

Answer: (A)

The concept here is using heart rate reserve (HRR) to prescribe exercise intensity with the Karvonen method. HRR combines your resting heart rate and your maximum heart rate to tailor intensity, rather than just using a straight percent of max HR. The target heart rate is calculated as HRrest plus a percentage of HRR, so the workout intensity stays aligned with your current fitness level.

Moderate intensity corresponds to about 40% to 59% of HRR. This range provides a steady, sustainable effort that improves aerobic capacity without being too easy or too hard. For example, if a patient has a resting heart rate of 60 bpm and a maximum of 180 bpm, the HRR is 120 bpm. The moderate zone would be 40% to 59% of 120, which is 48 to 70 bpm above rest, giving a target range of roughly 108 to 130 bpm. This illustrates why 40–59% of HRR is the appropriate choice for moderate intensity.

Ranges below this are lighter work, and ranges around or above 60% HRR approach vigorous intensity, so they don’t fit the moderate category.